This invention relates to crash attenuators intended to be placed alongside a roadway to protect the occupants of a vehicle that has left the roadway, and in particular to a self-restoring highway crash attenuator.
Carney U.S. Pat. No. 4,645,375 discloses a stationary impact attenuation system comprising a triangular array of vertically oriented metal cylinders mounted in front of a rigid object. An impacting vehicle deforms these metal cylinders, thereby reducing the maximum acceleration to which vehicle occupants are exposed. Since it uses metal tubes, the disclosed attenuation system is not self-restoring, and substantial replacement or refurbishment is required after each impact to restore the attenuation system to its original condition.
Tischer U.S. Pat. No. 5,607,252 discloses a highway collision containment system including a triangular array of flexible foam cylinders. The rear row of cylinders is held in place by stakes passing through the longitudinal axes of the cylinders, and the forward cylinders are held to the rearward cylinders by sheaths that are secured around the foam cylinders and to each other.
Stephens U.S. Pat. No. 5,314,261 discloses a vehicle crash cushion including an array of rubber cylinders that are secured together and to a wall. These cylinders are protected from contact with impacting vehicles by an array of panels 12 interposed between the rubber cylinders and the roadway. In the disclosed system, the rubber cylinders control the position of the panels 12, and it is the panels 12 that actually come into contact with an impacting vehicle.
In spite of the work described above, a need presently exists for a restorable crash attenuator that is simple to fabricate and to install, that provides an improved deceleration profile to an impacting vehicle, and that substantially restores itself to its original position after at least some impacts.
The preferred crash attenuator described below includes an array of resilient, self-restoring, polymeric tubes. Each of these tubes is characterized by a respective longitudinal axis and a respective wall thickness. The array includes at least three rows of tubes, and each row includes at least three tubes. The rows include a back row positioned closest to a rigid object, and a front row positioned farthest from the rigid object. Adjacent ones of the tubes are secured directly to one another, preferably by threaded fasteners, and the tubes of the back row are secured to the rigid object by other fasteners.
The preferred highway crash attenuator described below uses tubes with a substantially greater wall thickness for the front row than for the remaining rows. Also, the preferred crash attenuator uses an equal number of tubes in each of the rows, such that the array is rectangular rather than triangular, and such that the array defines two opposed sides extending between the front and the back row and a front comprising the front row. The tubes themselves form the outermost surfaces of the crash attenuator at the two sides and at the front, and the need for a supporting or protecting framework such as the panels 12 of the Stephens patent is thereby eliminated. Other array shapes and other distributions of wall thickness in the array are possible.
The foregoing paragraphs have been provided by way of general introduction, and they are not intended to limit the scope of the following claims.